1. Field of the Invention
The present invention relates to laser welding method.
2. Description of the Related Art
A filler wire may be used as filler metal in order to weld a welding object portion by projecting laser beam (for example, Japanese Patent Application Laid-Open No.HEI10-263862). That is, the filler wire is fed to this welding object portion while projecting laser beam to the welding object portion so as to fuse this filler wire, thereby supplementing insufficiency of molten metal.
In some case, welding is carried out on an object, which is already subjected to preliminary welding or a structure having a step or the like (for example, FIGS. 1, 7). In this case, there is a fear that the filler wire cannot be supplied to the welding object portion because of the preliminary welding portion 11 and the step portion 12. That is, the filler wire may interfere with the preliminary welding portion 11, so that its operation maybe changed or sticking occurs. Consequently, sometimes, the filler wire may fail to be settled or a front end portion of the filler wire may be fixed to the solidified wall (wall produced by solidification of the molten welding portion). If the filler wire is supplied from forward of laser beam, it is sometimes difficult to dispose a sensor for copying a welding line.
Accordingly, the present invention has been achieved to solve the above-described problems and therefore, an object of the present invention is to provide a laser welding method capable of supplying a filler wire to a welding object portion in a stabilized condition so as to stabilize welding quality.
To achieve the above object, according to a first aspect of the present invention, there is provided a laser welding method for supplying a filler wire 4 to a welding object portion 5 while projecting laser beam 2 to the welding object portion 5, wherein the filler wire is supplied obliquely from forward or backward in a welding advance direction such that an angle between the supplying direction and beam axis L of the laser beam 2 is less than 45xc2x0.
According to the laser welding method of the first aspect, even if there is a preliminarily welded portion or a stepped portion, the laser beam is unlikely to be interfered with the preliminarily welded portion or the stepped portion because an angle between the supplying direction of the filler wire 4 and beam axis of the laser beam 2 is less than 45xc2x0. Consequently, the filler wire 4 can be supplied to a welding object portion 5 in a stabilized condition so as to stabilize welding quality.
According to a second aspect of the present invention, the filler wire 4 is supplied from backward of the laser beam 2 with respect to the welding advance direction.
According to the second aspect of the present invention, the filler wire 4 is not disposed forward in the welding advance direction. Thus, a welding line copy sensor can be provided forward in the welding advance direction so that it is located in the vicinity of the laser beam 2. As a result, a highly accurate welding line copy can be achieved.
According to a third aspect of the present invention, the laser beam 2 is woven in a direction substantially perpendicular to the welding advance direction.
According to third aspect of the present invention, even if the welding object portion 5 has a gap portion, that gap portion can be joined together securely. Further, a deflection of an irradiation position of the laser beam 2 can be absorbed, thereby suppressing a fusion failure of the welding object portion 5.
According to a fourth aspect of the present invention, Vw/Fxe2x89xa62D/sin xcex8 is established when an angle between the beam axis and a supplying direction of the filler wire is xcex8, the diameter of key hole is D, supplying speed of the filler wire 4 is Vw and weaving frequency of the laser beam is F.
According to the fourth aspect of the present invention, the laser beam 2 is irradiated to a substantially entire length of the filler wire 4 to be supplied and therefore, a non-molten portion of the filler wire 4 does not arrive at a solidified wall, so that sticking can be avoided thereby leading to stabilization of welding quality.